Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P16104 (H2AX)
 3,930 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Efficient repair of DNA double-strand breaks depends on the intact signaling cascade, comprising molecules involved in DNA damage signal pathways and checkpoints. Budding yeast Rad9 (scRad9) is required for activation of scRad53 (mammalian homolog Chk2) and transduction of the signal further downstream in this pathway. In the search for a mammalian homolog, three proteins in the human data base, including BRCA1, 53BP1, and nuclear factor with BRCT domains protein 1 (NFBD1), were found to share significant homology with the BRCT motifs of scRad9. Because BRCA1 and 53BP1 are involved in DNA damage responses, a similar role for NFBD1 was tested. We show that NFBD1 is a 250-kDa nuclear protein containing a forkhead-associated motif at its N terminus, two BRCT motifs at its C terminus, and 13 internal repetitions of a 41-amino acid sequence. Five minutes after gamma-irradiation, NFBD1 formed nuclear foci that colocalized with the phosphorylated form of H2AX and Chk2, two phosphorylation events known to be involved in early DNA damage response. NFBD1 foci are also detected in response to camptothecin, etoposide, and methylmethanesulfonate treatments. Deletion of the forkhead-associated motif or the internal repeats of NFBD1 has no effect on DNA damage-induced NFBD1 foci formation. Conversely, deletion of the BRCT motifs abrogates damage-induced NFBD1 foci. Ectopic expression of the BRCT motifs reduced damage-induced NFBD1 foci and compromised phosphorylated Chk2- and phosphorylated H2AX-containing foci. These results suggest that NFBD1, like BRCA1 and 53BP1, participates in the early response to DNA damage.
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PMID:NFBD1, a novel nuclear protein with signature motifs of FHA and BRCT, and an internal 41-amino acid repeat sequence, is an early participant in DNA damage response. 1247 77

NFBD1/KIAA0170 is a nuclear factor with an N-terminal FHA (forkhead-associated) domain and a tandem repeat of BRCT (breast cancer susceptibility gene-1 C terminus) domains, both of which are present in a number of proteins involved in DNA repair and/or DNA damage signaling pathways. We have investigated the association of NFBD1 with DNA damage responses. We found that the NFBD1 transcript is abundant in the testis relative to other tissues. NFBD1 is a chromatin-associated protein and is modified in G(2)/M phase or after DNA damage. NFBD1 phosphorylation in response to ionizing radiation (IR) was ATM-dependent. NFBD1 exhibited diffuse nuclear staining in the majority of untreated cells analyzed by indirect immunofluorescence and formed discrete nuclear foci after exposure to IR, UV radiation, and hydroxyurea treatment. IR induced NFBD1 foci within 1 min. The foci colocalized with gamma-H2AX foci, which have been previously shown to localize at sites of DNA double-strand breaks. IR-induced NFBD1 foci also colocalized with 53BP1 and MRE11/RAD50 foci. Taken together, these results suggest that NFBD1 is a mediator of DNA damage-dependent signaling.
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PMID:NFBD1/KIAA0170 is a chromatin-associated protein involved in DNA damage signaling pathways. 1249 69

Signaling pathways in response to DNA double strand breaks involve molecular cascades consisting of sensors, transducers, and effector proteins that activate cell cycle checkpoints and recruit repair machinery proteins. NFBD1 (a nuclear factor with BRCT domains protein 1) contains FHA (forkhead-associated), BRCT (breast cancer susceptibility gene 1 carboxyl terminus) domains, and internal repeats and is an early participant in nuclear foci in response to IR. To elucidate its role in the response pathways, small interfering RNA (siRNA) directed against NFDB1 in human cells demonstrated that its absence is associated with increased radio-sensitivity and delayed G(2)/M transition, but not G(1) to S. NFBD1 associates with nuclear foci within minutes following IR, a property similar to histone H2AX, 53BP1, and Chk2, which are all early participants in the DNA damage signaling cascade. Temporal studies show that H2AX is required for the foci positive for NFBD1, but NFBD1 is not needed for 53BP1- and H2AX-positive foci. NFBD1, together with 53BP1, plays a partially redundant role in regulating phosphorylation of the downstream effector protein, Chk2, since abrogation of both diminishes phosphorylated Chk2 in IR-induced foci. These results place NFBD1 parallel to 53BP1 in regulating Chk2 and downstream of H2AX in the recruitment of repair and signaling proteins to sites of DNA damage.
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PMID:NFBD1, like 53BP1, is an early and redundant transducer mediating Chk2 phosphorylation in response to DNA damage. 1255 34

MRE11, RAD50 and NBS1 form a highly conserved protein complex (the MRE11 complex) that is involved in the detection, signalling and repair of DNA damage. We identify MDC1 (KIAA0170/NFBD1), a protein that contains a forkhead-associated (FHA) domain and two BRCA1 carboxy-terminal (BRCT) domains, as a binding partner for the MRE11 complex. We show that, in response to ionizing radiation, MDC1 is hyperphosphorylated in an ATM-dependent manner, and rapidly relocalizes to nuclear foci that also contain the MRE11 complex, phosphorylated histone H2AX and 53BP1. Downregulation of MDC1 expression by small interfering RNA yields a radio-resistant DNA synthesis (RDS) phenotype and prevents ionizing radiation-induced focus formation by the MRE11 complex. However, downregulation of MDC1 does not abolish the ionizing radiation-induced phosphorylation of NBS1, CHK2 and SMC1, or the degradation of CDC25A. Furthermore, we show that overexpression of the MDC1 FHA domain interferes with focus formation by MDC1 itself and by the MRE11 complex, and induces an RDS phenotype. These findings reveal that MDC1-mediated focus formation by the MRE11 complex at sites of DNA damage is crucial for the efficient activation of the intra-S-phase checkpoint.
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PMID:MDC1 is required for the intra-S-phase DNA damage checkpoint. 1260 3

NFBD1/MDC1 (mediator of DNA damage checkpoint 1) is a nuclear factor with an amino-terminal FHA (forkhead-associated) domain and a tandem repeat of BRCT (breast cancer susceptibility gene-1 carboxyl terminus) domains. We have previously shown that NFBD1 is an early participant in DNA damage signaling pathways and that ionizing radiation-induced nuclear foci (IRIF) of NFBD1 colocalize with several DNA checkpoint signaling and repair factors. We report here that NFBD1 physically associates with ATM, p53, components of the MRE11-RAD50-NBS1 (MRN) complex, and gamma-H2AX. An overexpressed FHA domain-containing fragment of NFBD1 binds to endogenous NFBD1 and components of the MRN complex, but not to gamma-H2AX. This fragment interferes with IRIF formation by endogenous NFBD1, MRE11, or NBS1. A BRCT domain-containing fragment of NFBD1 binds to gamma-H2AX and 53BP1, but not to components of the MRN complex, and abolishes IRIF formation by NFBD1, MRE11, NBS1, 53BP1, CHK2 phospho-T68, gamma-H2AX, and possible ATM/ATR substrates recognized by anti-phospho-SQ/TQ antibody. These results suggest that NFBD1 is an ATM/ATR-dependent organizer that recruits DNA checkpoint signaling and repair proteins to the sites of DNA damage.
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PMID:NFBD1/MDC1 regulates ionizing radiation-induced focus formation by DNA checkpoint signaling and repair factors. 1451 63

Mdc1/NFBD1 controls cellular responses to DNA damage, in part via interacting with the Mre11-Rad50-Nbs1 complex that is involved in the recognition, signalling, and repair of DNA double-strand breaks (DSBs). Here, we show that in live human cells, the transient interaction of Nbs1 with DSBs and its phosphorylation by ATM are Mdc1-independent. However, ablation of Mdc1 by siRNA or mutation of the Nbs1's FHA domain required for Mdc1 binding reduced the affinity of Nbs1 for DSB-flanking chromatin and caused aberrant pan-nuclear dispersal of Nbs1. This occurred despite normal phosphorylation of H2AX, indicating that lack of Mdc1 does not impair this DSB-induced chromatin change, but rather precludes the sustained engagement of Nbs1 with these regions. Mdc1 (but not Nbs1) became partially immobilized to chromatin after DSB generation, and siRNA-mediated depletion of H2AX prevented such relocalization of Mdc1 and uncoupled Nbs1 from DSB-flanking chromatin. Our data suggest that Mdc1 functions as an H2AX-dependent interaction platform enabling a switch from transient, Mdc1-independent recruitment of Nbs1 to DSBs towards sustained, Mdc1-dependent interactions with the surrounding chromosomal microenvironment.
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PMID:Mdc1 couples DNA double-strand break recognition by Nbs1 with its H2AX-dependent chromatin retention. 1520 65

Mammalian ATR and ATM checkpoint kinases modulate chromatin structures near DNA breaks by phosphorylating a serine residue in the carboxy-terminal tail SQE motif of histone H2AX. Histone H2A is similarly regulated in Saccharomyces cerevisiae. The phosphorylated forms of H2AX and H2A, known as gamma-H2AX and gamma-H2A, are thought to be important for DNA repair, although their evolutionarily conserved roles are unknown. Here, we investigate gamma-H2A in the fission yeast Schizosaccharomyces pombe. We show that formation of gamma-H2A redundantly requires the ATR/ATM-related kinases Rad3 and Tel1. Mutation of the SQE motif to AQE (H2A-AQE) in the two histone H2A genes caused sensitivity to a wide range of genotoxic agents, increased spontaneous DNA damage, and impaired checkpoint maintenance. The H2A-AQE mutations displayed a striking synergistic interaction with rad22Delta (Rad52 homolog) in ionizing radiation (IR) survival. These phenotypes correlated with defective phosphorylation of the checkpoint proteins Crb2 and Chk1 and a failure to recruit large amounts of Crb2 to damaged DNA. Surprisingly, the H2A-AQE mutations substantially suppressed the IR hypersensitivity of crb2Delta cells by a mechanism that required the RecQ-like DNA helicase Rqh1. We propose that gamma-H2A modulates checkpoint and DNA repair through large-scale recruitment of Crb2 to damaged DNA. This function correlates with evidence that gamma-H2AX regulates recruitment of several BRCA1 carboxyl terminus domain-containing proteins (NBS1, 53BP1, MDC1/NFBD1, and BRCA1) in mammals.
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PMID:Histone H2A phosphorylation controls Crb2 recruitment at DNA breaks, maintains checkpoint arrest, and influences DNA repair in fission yeast. 1522 25

The protein MDC1/NFBD1 contains a forkhead-associated (FHA) domain and two BRCA1 carboxyl-terminal (BRCT) domains. It interacts with several proteins involved in DNA damage repair and checkpoint signalling, and is phosphorylated in response to DNA damage and during mitosis. Upon treatment of cultured human cells with DNA damaging agents, MDC1/NFBD1 translocates to sites of DNA lesions, where it collaborates with other proteins and with phosphorylated histone H2AX to mediate the accumulation of checkpoint and repair factors into nuclear foci. Down-regulation of MDC1/NFBD1 expression levels by small interfering RNA (siRNA) renders cells hyper-sensitive to DNA damaging agents and leads to defects in cell cycle checkpoint activation and apoptosis. Thus, MDC1/NFBD1 appears to be a key regulator of the DNA damage response in mammalian cells.
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PMID:MDC1/NFBD1: a key regulator of the DNA damage response in higher eukaryotes. 1527 81

Cellular functions of the NimA-related mammalian kinase Nek1 have not been demonstrated to date. Here we show that Nek1 is involved early in the DNA damage response induced by ionizing radiation (IR) and that Nek1 is important for cells to repair and recover from DNA damage. When primary or transformed cells are exposed to IR, Nek1 kinase activity is increased within 4 minutes, and Nek1 expression is up-regulated shortly thereafter and sustained for hours. At the same early time frame after IR that its kinase activity is highest, a portion of Nek1 redistributes in cells from cytoplasm to discrete nuclear foci at sites of DNA double-strand breaks. There it colocalizes with gamma-H2AX and NFBD1/MDC1, two key proteins involved very early in the response to IR-induced DNA double-strand breaks. Finally, Nek1-deficient fibroblasts are much more sensitive to the effects of IR-induced DNA damage than otherwise identical fibroblasts expressing Nek1. These results suggest that Nek1 may function as a kinase early in the DNA damage response pathway.
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PMID:NIMA-related protein kinase 1 is involved early in the ionizing radiation-induced DNA damage response. 1560 34

Budding yeast Rad9 (scRad9) plays a central role in mediating Mec1-dependent phosphorylation by recruiting its downstream substrates. The human scRad9 orthologues 53BP1 and NFBD1 associate with ionizing radiation-induced foci (IRIF) at sites of DNA repair. RNAi-based gene silencing of 53BP1 or NFBD1 has shown impaired phosphorylation of SQ/TQ [ataxia-telangiectasia mutated/ATM and Rad3-related (ATM/ATR) substrates] at IRIF, intra-S, and G(2)-M checkpoints and has thereby revealed essential roles for 53BP1 and NFBD1 in the DNA damage signaling pathway. Whether 53BP1 and NFBD1 are required for activation of kinases and/or for recruitment of substrates at IRIF, however, is not clear. Here we show that both 53BP1 and NFBD1 are required for recruitment of ATR to DNA damage sites, as well as for ATR-dependent phosphorylation in response to DNA damage. NFBD1 is not required for ssDNA generation at DNA damage sites and is not recruited by replication protein A (RPA)-coated ssDNA. We therefore show that recruitment of NFBD1 and/or 53BP1, the factors downstream of H2AX, is independent of ssDNA generation and RPA coating, whereas both ssDNA and RPA coating play key roles in regulation of the ATR-dependent pathway. These novel findings help clarify where NFBD1 functions in DNA damage early responses.
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PMID:NFBD1/Mdc1 mediates ATR-dependent DNA damage response. 1573 98


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